The use of metal detectors is quite wide, stations, airports, schools, etc., have its appearance, in the working method of metal detectors, metal detector manufacturers introduce industrial metal detectors can have two ways of device, can be on the conveyor belt conveyor products above or below the device plate coil, But more flexible detectors should pass the product through a coil and install the coil in a metal housing.
This more flexible coil type is typically fitted with three coils, a central transmitting coil and two receiving coils wound in opposite directions within a probe. The oscillator connected to the central coil generates a high-frequency magnetic field, and the two opposite wound acceptance coils are connected to each other so that the induced voltage generated by them can be self-cancelled when the magnetic field is not disturbed.
To achieve good flexibility, the aperture size of the metal detector should be matched to the specific product size. Too large an aperture risks weakening the "signal", while too small an aperture will make it difficult for the product to pass on the conveyor belt. The flexibility of the detector is usually derived from an insensitive geometric point measured from the geometric center of the aperture.
When the metal contaminated product passes by, the implied metal object interferes with the magnetic field of the detector, and the output signal of the two receiving coils cannot cancel each other, thus detecting the presence of metal impurities.
Metal detectors use the principle of electromagnetic induction, using an alternating current passing through a coil to create a rapidly changing magnetic field. This magnetic field can induce eddy currents inside metal objects. The eddy current will generate a magnetic field, which in turn affects the original magnetic field, causing the detector to emit a sound.
There are three main categories of metal detectors: electromagnetic induction type, X-ray detection type, microwave detection type, which are electronic instruments for metal detection and can be applied in many fields. In the military, metal detectors can be used to detect metal; In the field of security, it is possible to detect carried or hidden weapons and instruments of crime; In terms of archaeology, it is possible to detect the tombs where metal objects are buried, and find the gold and silver treasures and jewelry or other metal products in the tombs; In engineering, it can be used to detect underground metal buried objects, such as pipelines, pipelines, etc. In mineral exploration, it can be used to detect and discover natural gold particles; In industry, it can be used for online monitoring, such as removing metal debris in cotton, coal, and food.